package com.example.flinkcourse.lesson5.evolution;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.flink.api.common.functions.MapFunction;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Schema Evolution 实现
 */
public class SchemaEvolution {
    private static final Logger LOG = LoggerFactory.getLogger(SchemaEvolution.class);
    private static final ObjectMapper objectMapper = new ObjectMapper();
    
    /**
     * 创建 Schema Evolution 处理函数
     *
     * @return MapFunction
     */
    public static MapFunction<String, String> createEvolution() {
        return new MapFunction<String, String>() {
            @Override
            public String map(String value) throws Exception {
                try {
                    // 解析 JSON 数据
                    JsonNode jsonNode = objectMapper.readTree(value);
                    
                    // 获取操作类型
                    String op = jsonNode.get("op").asText();
                    
                    // 获取表名
                    String tableName = jsonNode.get("source").get("table").asText();
                    
                    // 处理 Schema 变更
                    if ("c".equals(op)) {  // 创建表
                        handleCreateTable(jsonNode, tableName);
                    } else if ("u".equals(op)) {  // 更新表
                        handleUpdateTable(jsonNode, tableName);
                    }
                    
                    return objectMapper.writeValueAsString(jsonNode);
                } catch (Exception e) {
                    LOG.error("Schema Evolution 处理失败: {}", value, e);
                    return value;
                }
            }
        };
    }
    
    /**
     * 处理创建表操作
     */
    private static void handleCreateTable(JsonNode jsonNode, String tableName) {
        LOG.info("处理创建表操作: {}", tableName);
        // TODO: 实现创建表逻辑
    }
    
    /**
     * 处理更新表操作
     */
    private static void handleUpdateTable(JsonNode jsonNode, String tableName) {
        LOG.info("处理更新表操作: {}", tableName);
        // TODO: 实现更新表逻辑
    }
} 